Having determined the X-ray crystal structures of Glycera and lamprey hemoglobins at 2.5 and 2.0 Angstrom units respectively, it is proposed to refine these structures both with and without ligands at 1.5 Angstrom units resolution. The aim is to define as objectively and precisely as possible the structural changes that accompany the binding of ligands. Thus, details will be obtained about the stereochemical events that occur in these heme pockets and additional data will become available to complement that already known from Chironomus hemoglobin, sperm whale myoglobin and human hemoglobin. It is proposed to determine the crystal structure of polymeric lamprey hemoglobin, complete the low resolution structures of a subunit of Limulus hemocyanin and liganded Trout hemoglobins I and IV.